Method for producing a hollow fastener element, electrical connections and component assembly

ABSTRACT

A method for providing an electrically conductive connection between an electric terminal device having a cavity and a sheet metal part. A hollow fixing element is riveted to the sheet metal part to prevent torsion producing an electrically conductive connection between the fixing element and the sheet metal part. The assembled component is then provided with an electrically non-conductive or poorly conductive protective coating. A receptacle for the electric terminal device is configured near the front face of the fixing element, to which the electrical terminal device is attached. The receptacle prevents the torsion of the terminal device in relation to the fixing element. The sheet metal part and a thread forming or cutting screw is screwed through the cavity of the electric terminal device into the hollow fixing element to form or cut a thread. The invention also relates to a corresponding fixing element and an assembled component.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. patent application Ser. No.12/119,882 filed May 13, 2008, which issued as U.S. Pat. No. 8,083,451on Dec. 27, 2011, which claims priority from a divisional applicationSer. No. 10/528,279 filed Aug. 18, 2005, which issued as U.S. Pat. No.7,988,394 on Aug. 2, 2011, which claims priority of PCT/EP03/007436filed Jul. 9, 2003 and of German patent application No. 102 43 759.9filed Sep. 20, 2002 and is a continuation-in-part application of U.S.patent application Ser. No. 10/472,648 filed Mar. 30, 2004 which issuedas U.S. Pat. No. 7,367,767 on May 6, 2008, which claims priority ofPCT/EP02/03187 filed Mar. 21, 2002 and of German patent application No.101 14 200.5 filed Mar. 23, 2001, and the complete contents of all ofthe applications are incorporated herein by reference.

The present invention relates to a method for producing an electricallyconductive connection between an electrical terminal device having acutout, such as a cable shoe, and a sheet metal part, in which a hollowfastener element is rotationally fixedly riveted to the sheet metal partand an electrically conductive connection is hereby produced between thefastener element and the sheet metal part and the so manufacturedcomponent assembly is subsequently provided with an electricallynon-conductive or poorly conductive protective coating such as forexample a paint layer or a powder coating. Furthermore, the inventionrelates to a fastener element for the use of a method and a componentassembly consisting of a fastener element and a sheet metal part.

A fastener element of the initially named kind is for example known fromEP-A-539743.

The component assembly which arises when the fastener element isattached to a sheet metal part can be provided, in accordance with theinitially named method, with a protective coating, such as for example apaint layer or powder coating. This is not expressly described inEP-A539743.

The nut element of EP-A-539793 cannot be attached to a sheet metal partin self-piercing manner but rather the sheet metal part must beprepierced. Furthermore, the sheet metal preparation described inEP-A539793 includes the generation of an axially projecting ring lip inthe sheet metal part which hounds an opening into which the rivetsection of the fastener element must be inserted. During this operationthe ring lip projects at the side of the sheet metal part from which thefastener element is attached. The projecting lip with the pre-preparedopening signifies in practice that the fastener element must be alignedwith high accuracy with respect to the sheet metal part in order toensure an orderly attachment of the fastener element.

Furthermore, in the component assembly Which arises when a fastenerelement in accordance with EP-A-539793 is attached to a sheet metalpart, the problem exists that the protective coating applied to thecomponent assembly makes it difficult to produce an electricallyconductive connection from a cable shoe to the component assembly. Theprotective coating must be removed by intensive work from the criticalposition or the component must be so covered over at the position wherethe cable shoe is to be attached, likewise with intensive work, so thatthe protective coating which is deposited there can be removed with thecover. It is furthermore unfavourable in this method that, on removingthe cover, exposed surface regions of the fastener element exist whichare no longer provided with the protective coating and which corrode inthe long term. This is not only ugly but rather the corrosion whichprogresses can lead to an undesired deterioration of the electricalcontact between the terminal device and the fastener element.

BRIEF SUMMARY OF THE INVENTION

The object of the present invention is to so improve a method or afastener element and a component assembly of the initially named kindthat an electrical connection of high quality can be achieved betweenthe electrical terminal device and the sheet metal part in acost-favourable manner without the protective coating impairing thequality of the electrical connection and without complicated measureshaving to be taken in order to remove the protective coating.

in order to satisfy this object there is provided, in accordance withthe invention, a method of the initially named kind which ischaracterized in that a mount for the electrical terminal device isformed in the region of the end face of the fastener element to whichthe electrical terminal device is attached and prevents a rotation ofthe terminal device relative to the fastener element and the sheet metalpart and in that a thread forming or thread cutting screw is screwedthrough the cut-out of the electrical terminal device and into thehollow fastener element and there forms or cuts a thread by the screw-inmovement.

Furthermore, in accordance with the invention, a fastener element isprovided for the electrically conductive attachment of an electricalterminal device such as a cable shoe to a sheet metal part which ischaracterized in that the hollow fastener element has a head part and arivet section, with the rivet section merging via a contact surface forthe sheet metal part into the head part and with features providingsecurity against rotation being provided at the contact surface and/orat the rivet section, wherein the hollow fastener element has a bore,for example a smooth cylindrical bore, at a point at which a thread isto be formed by screwing—in a thread cutting or thread forming screw andin that a mount for the rotationally secure attachment of the electricalconnection device to the fastener element is provided at the end face ofhead part remote from the rivet section.

Through the attachment of such a fastener element to a sheet metal parta component assembly then results in accordance with the inventionconsisting of a sheet metal part and a hollow fastener element attachedto it via a rivet connection, wherein the fastener element isrotationally fixedly secured to the sheet metal part by means offeatures providing security against rotation and the fastener elementand the sheet metal part are jointly coated with an electricallynon-conductive or poorly conductive protective coating and anelectrically conductive path is provided between the fastener elementand the sheet metal part in the region of the rivet connection and/orthe features providing security against rotation. The component assemblyis characterized in that fastener element has a smooth cylinder bore forreceiving a thread forming or cutting screw and in that the fastenerelement has a mount at the end face remote from the rivet connection forthe rotationally secure attachment of the electrical terminal device.

The fastener element is preferably attached in self-piercing manner tothe sheet metal part, that is to say that either the rivet section canbe formed as a piercing and riveting section or a tubular part of thefastener element in the region of the riveting section can be used asthe piercing device in order to pierce a hole in the sheet metal part.The force which is required in order to carry out the piercing processcan for example be delivered as usual during the attachment of fastenerelements to sheet metal parts by a press which takes care of thecarrying out of the attachment process. Alternatively, it can be madeavailable by a robot or other types of tools. The use of fastenerelements in self-piercing embodiments not only has the advantage that inthis way one working step in the sense of the prepiercing of the sheetmetal part can be avoided, but rather the piercing process also ensuresthat clear metallic surfaces are present at the fastener element and atthe sheet metal part which take care of a low transition resistancebetween the fastener element and the sheet metal part, i.e. that a highquality electrical connection is present at the corresponding points.

Through the rotationally secure attachment of the fastener element tothe sheet metal part a high quality electrical connection is likewiseachieved between the fastener element and the sheet metal part in theregion of the features providing security against rotation whichnormally have the form of ribs and which can optionally be made withsharp edges in order to ensure an even better electrical transition tothe sheet metal part. If the component assembly so produced is providedwith an electrically non-conductive or poorly conductive protectivelayer the electrically conducting transition region between thecomponent assembly and the sheet metal part is sealed off from theoutside so that corrosion at these points need not be feared. That is tosay, conductive transitions arise between the piercing section of thefastener element and the sheet metal part and between the featuresproviding security against rotation and the sheet metal part atpositions where the elements lie so tightly against one another that apenetration of the protective coating at these points do not occur. Thesealing of the component assembly by the protective layer also preventsoxygen and humidity reaching these conductive transitions wherebycorrosion at these points is prevented long term.

The protective coating however fully covers over the outwardly disposedsurface regions of the fastener element and frequently also penetratesinto the bore of the hollow fastener element, in particular, whenelectrostatic aids are used during the painting. At this point it shouldbe briefly mentioned that the said bore does not strictly speaking haveto be produced by a boring tool, but can rather also be produced by coldheading tools or by piercing processes or in other ways. The designationbore is thus to be understood. in such a way that it is not restrictedto a specific manufacturing process.

Through the use of a thread cutting or forming screw in order to screwthe electrical terminal device to the exposed end face of the fastenerelement an intensive mechanical working of the bore of the fastenerelement by the screw takes place on the one hand, so that high qualityelectrical transitions between the screw and the fastener element arealso provided here. Any protective coating which is present in the boreis at least partly scraped away or cut away by the screwing in of thescrew and a considerable contact pressure arises between the screw andthe fastener element so that a high quality electrical connection isalso present in these regions in the long term. Any residues ofprotective coatings which are trapped in the region of the thread takecare of a sealing of the thread and also contribute to the protectionagainst corrosion. There is no need to scratch away or otherwise removethe protective coating from the end face of the fastener element priorto the attachment of the electrical terminal device. The electricalterminal device sits at its one side on this protective coating at theend face of the fastener element. However the head of the screw forms ahigh quality electrical connection to the electrical terminal device.Since the electrical terminal device is rotationally securely held tothe fastener element a certain amount of slippage arises between thehead of the screw and the electrical terminal device during thetightening of the screw which takes care of fresh metallic surfaces atthis point so that a high quality electrical connection also ariseshere.

The electrically conductive connection thus leads from the electricallyterminal device via the screw into the fastener element in the region ofthe thread and from the metallic fastener element via the featuresproviding security against rotation and surface regions in the vicinityof the pierced hole into the sheet metal part. The sheet metal part isthen normally incorporated into a vehicle body or into a housing whichcan be termed earth.

Since a thread cutting or thread forming screw is used and since thebore of the hollow fastener element can be occupied at least in partwith a protective coating a considerable friction arises between thescrew and the fastener element during attachment of the screw so thatconsiderable torques are exerted on the fastener element. The securityagainst rotation between the fastener element and the sheet metal partmust therefore be so designed that it can withstand such rotary forces.Also the application of the corresponding rotary forces via the toolthat is used frequently leads to a pronounced button out moment at theelement itself so that the connection between the fastener element andthe sheet metal part should be secure against such button out moments,i.e. a considerable button out resistance that should he present.

This requirement is satisfied by a fastener element which ischaracterized in that a tubular guide section is disposed concentric tothe tubular rivet section and radially within the latter, with a ringgap being present between the guide section and the rivet section andwith the guide section projecting beyond the free end of the rivetsection.

Since a tubular guide section is disposed concentric to the tubularrivet section and radially within the latter, with the guide sectionprojecting beyond the second end of the rivet section, care has beentaken, in accordance with the invention, when using the fastener elementwith a prepierced sheet metal, that the guide section moves into thehole of the prepierced sheet metal, optionally with dilation of thehole, and takes care of centring of the fastener element relative to thepre-manufactured hole or to the dilated, hole. Since the guide processtakes place before the subsequent dilation of the hole by the rivetsection and the subsequent beading over of the rivet section it is alsoensured that a high quality mechanical and electrical connection alwaysarises between the fastener element and the sheet metal part.

Should a pre-piercing of the sheet metal part be provided, which isbasically possible, but which is not however preferred, then thispre-piercing can also be effected in such a way that no projectingring-lip is present at the side of the sheet metal part from which thefastener element is introduced, which likewise facilitates the alignmentof the fastener element with the sheet metal part.

In the present invention it is particularly favourable that the guidesection of the fastener element can be formed as a piercing section,with the fastener element being introduced in self-piercing manner intothe sheet metal part, so that a pre-piercing is not necessary at all andthe requirements placed on the alignment of the fastener element withthe sheet metal part are even lower. Through the self-piercing design ofthe fastener element a favourably priced manufacture of the componentassembly is also achieved because the operation of pre-piercing thesheet metal part is omitted. in this way the method for the attachmentof the fastener element to the sheet metal part is also simplified.

At this point reference should briefly be made to DE-C-3446978 andDEC-3447006. DE-C-3446978 describes amongst other things a nut elementwhich can be introduced in self-piercing manner into a sheet metal partwhereas DE-C-3447006 discloses a similarly conceived bolt element.Neither the nut element nor the bolt element in accordance with theabove-named German patent has a guide section in addition to the rivetsection, so that the rivet section has to execute both the piercingfunction and also the riveting function, which is ultimately morecomplicated and places more stricter requirements on the rivet sectionand on the die button that is used than in the case of the abovedesignated arrangement with separate riveting and piercing sections.Nevertheless a fastener element with a piercing and riveting section canbe exploited for the purpose of the present invention as will beexplained in more detail later.

It is particularly preferred if the free end of the wall of thering-like rivet section is rounded as seen in an axial section plane,both at the radially outer side and also at the radially inner side andfor example has a semicircular shape or a shape resembling an.arrow-tip.

As already indicated the guide section of the fastener element leadsduring the attachment of the fastener element to a sheet metal part, toa conical recess in the sheet metal part and indeed, in a pre-piercedsheet metal part, during the dilation of the hole by the guide sectionand, in a self-piercing embodiment of the fastener element, prior to thecutting out of a piercing slug by the guide section which forms apiercing section, with the conical recess then being dilated by theriveting section. The rounded embodiment of the outer wall of the rivetsection in the region of its free end is a favourable shape for thefurther dilation of the hole and the corresponding deformation of theconical wall of the recess. The rounded shape at the inner side of thefree end of the rivet section helps in contrast during the beading overof the rivet section which takes place in a correspondingly concavelyarched ring surface of the die button. This shape also makes it possiblefor the ring gap to be kept as small as possible without impairing theprocess of beading over the rivet section. Since the ring gap can bekept as small as possible and can indeed amount to 0 mm (which signifiesthat the inner wall of the rivet section contacts the outer periphery ofthe guide section) the diameter of the fastener element as a whole canbe kept as small as possible whereby material is saved and costs arereduced.

The ring gap preferably has a radial dimension in the range between 0 mmand approximately 3 mm. The ring gap preferably ends at an axial spacingin front of the ring-like contact surface at the rivet section side ofthe ring-like contact. surface. This design leads to a stable attachmentof the rivet section to the head part of the element and favours a firmattachment of the fastener element to the sheet metal part.

When the guide section is formed as a piercing section it preferably hasa ring-like cutting edge at its end remote from the contact surface andthis cutting edge cooperates with a correspondingly shaped cutting edgeof a central bore of a die button in order to punch out a clean piercingslug from the sheet metal part during the attachment of the fastenerelement to the sheet metal part.

It is particularly preferred when features providing security againstrotation are disposed in the region of the contact surface and/or at therivet section and/or at the jacket surface of the head part adjacent tothe contact surface. When the features providing security againstrotation are provided in the region of the jacket surface of the headpart then they can be produced by a. polygonal or grooved form of thejacket surface. The features providing security against rotation can beformed by noses or by groove-like recesses in the region of thering-like contact surface and/or at the rivet section and optionally atthe jacket surface.

When noses providing security against rotation are provided then thesecan be present in raised form at the contact surface and at the rivetsection in the region of the transition from the contact surface intothe rivet section.

The mount for the electrical terminal device is preferably formed by at5 least one projection with projects beyond the end face of the fastenerelement. Here a projection, for example, formed as a lug, is sufficientin order to prevent a rotation of the electrical terminal device, forexample in the form of a cable shoe, since with an initial rotation ofthe cable shoe the connection region for the cable then enters intocontact against a flank of the projection or of the lug and prevents afurther rotation of the electrical terminal device. It is even morefavourable when the fastener element is executed with two projectionswhich are formed by two lugs having a spacing from one another which arearranged to the side of the bore of the hollow fastener element. Theregion of the cable shoe which receives the cable can then be positionedbetween the two lugs and the relative rotation between the cable shoeand the fastener element can be reduced to a minimum which is determinedby the spacing between the two lugs. On the other hand, the two lugsprovide two open regions in which the cable connection region of thecable shoe can be selectively disposed. Naturally a plurality ofprojections can also be provided, whereby a plurality of open regionsare provided between two lugs in each case, so that a plurality ofpossible orientations of the cable shoe are present.

The projection can also extend around the bore of the fastener elementand be made polygonal in its external outline. For example externaloutlines in triangular, square, hexagonal or octagonal form can beconsidered, with the octagonal form being particularly preferred becauseit permits a plurality of possible orientations of a correspondinglydesigned cable shoe.

Further preferred embodiments of the method of the invention, of thefastener element and also of the component assembly can be seen from theaccompanying subordinate claims and also from the further description ofembodiments.

The invention will be explained in more detail in the following by wayof example and with reference to embodiments and to the drawings.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 shows a side view of a hollow fastener element in accordance withthe invention,

FIG. 2 shows a plan view of the upper end face of the fastener elementof FIG. 1,

FIG. 3 shows a perspective illustration of the fastener element of theFIGS. 1 and 2,

FIG. 4 shows a representation partly sectioned in the longitudinaldirection of the fastener element of the FIGS. 1 to 3 in the startingstage of the attachment of the fastener element to a sheet metal partusing a die button,

FIG. 5 shows a representation similar to FIG. 4 but at a later phase ofthe attachment of the fastener element to the sheet metal part,

FIG. 6 shows a representation similar to FIG. 5 but at a yet later stageof the attachment of the fastener element to the sheet metal part,

FIG. 7 shows a representation similar to FIG. 6 after completion of theattachment of the functional element of the sheet metal part, and

FIG. 8 shows a component assembly of FIG. 7 after the removal from thetool for the manufacture of the component assembly.

FIG. 9 shows an alternative embodiment of the fastener element similarto the fastener element of FIGS. 1-8, but with a different mount for theelectrical terminal device, with FIG. 9 showing the element partly inside view and partly in longitudinal section,

FIG. 10 shows a plan view on the lower side of the fastener element ofFIG. 9,

FIG. 11 shows a perspective illustration of the fastener element ofFIGS. 9 and 10,

FIG. 12 shows a side view of the fastener element of FIGS. 9, 10 and 11,

FIG. 13 shows the detail Z in FIG. 9,

FIG. 14 shows the fastener element of FIG. 9 attached to a sheet metalpart,

FIG. 15 shows the component assembly of FIG. 14 with an electricalterminal device which is secured via a screw to the fastener element,

FIG. 16 shows a plan view of the electrical terminal device of FIG. 15prior to attachment to the fastener element of FIG. 15,

FIG. 17 shows a representation of a further embodiment of a fastenerelement in accordance with the invention partly in side view and partlyin a longitudinally sectioned view,

FIG. 18 shows a plan view on the top side of the fastener element ofFIG. 17 and

FIG. 19 shows the fastener element of FIGS. 17 and 18 after attachmentto a sheet metal part.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIGS. 1 to 4 the fastener element 10 shown there isprovided with a head part 14 having a ring-like contact surface 12 and atubular rivet section 16 provided at the side of the contact surface 12of the head part 14 and extending away from the head part 14. Thefastener element has a central longitudinal axis 11. A tubular guidesection 18 is arranged concentric to the tubular rivet section 16 andradially within the latter, with a ring gap 20 being provided betweenthe guide section 18 and the rivet section 16, the ring gap only beingvisible in FIG. 4.

As can likewise be seen from FIG. 4 the free end 22 of the wall of thering-like rivet section 16 is rounded when viewed in the axial sectionplane of FIG. 4 both at the radially outer side 24 and also at theradially inner side 26 and has here a rounded shape resembling anarrow-tip. The tip of shape resembling an arrow-tip could howeverlikewise be rounded, which would result in a semicircular shape, whichis however not shown.

In the illustration of FIG. 4 the ring gap has a radial dimension of 0mm i.e. the rivet section contacts the guide section 18 but is firstconnected to the guide section 18 at the position where the ring gap 20finishes at a short axial spacing “a” from the ring-like contact surface12.

The fastener element of FIGS. 1 to 4 is normally produced by a coldheading process, the basic principles of which are well known per se. Inorder to manufacture the rivet section which closely contacts the guidesection it can be necessary to first produce the rivet section with acertain radial spacing from the guide section by cold heading andsubsequently, in a further phase of the cold heading process, to pressthe rivet section against the guide section or to dilate the guidesection until it enters into contact with the rivet section or toachieve the reduction of the radial spacing by a combination of the twomeasures. It is favourable when the ring gap 20 has the smallestpossible radial width because this leads to a compact design of thefastener element and saves material.

The guide section 18 is formed here as a piercing section and has aring—20 like cutting edge 28 at its end remote from the contact surface12, i.e. at its free end.

The FIGS. 1 to 4 furthermore show features 30 providing security againstrotation in the region of the ring-like contact surface 12 and at therivet section 16, with the features providing security against rotationbeing formed here by noses which are present in raised form at thecontact surface 12 and at the rivet section 16 in the region of thetransition from the contact surface into the rivet section 16. The nosesproviding security against rotation shown here are provided with sideflanks 30 and 32 which lie in planes extending in the longitudinaldirection of the element.

The noses providing security against rotation are made with sharp edgesat 34 and 36 in FIGS. 1 and 4 and could instead be provided here withrounded edges. The noses providing security against rotation could alsobe realized by recesses in the contact surface or in the rivet section.The possibility also exists of giving the jacket surface 36 of the headpart 14 a polygonal or grooved shape. The hollow fastener element has asmoothed cylindrical bore which is disposed coaxial to the longitudinalaxis 11 of the fastener element and in this example is partly present inthe guide section 18.

The diameter of the smooth cylindrical bore is so dimensioned that byturning in a thread cutting or thread forming screw, such as is forexample explained in more detail with reference to FIG. 15, a thread ofthe desired size arises. For an M8 thread the diameter of 7.55 is forexample selected for a thread forming screw. For thread cutting screwsthe usually provided dimensions can likewise be selected.

A further special feature of the hollow fastener element of FIGS. 1 to 4is to be seen in the two lugs 40 which projects from the upper end faceof the element 10 and which can be produced by shifting material fromthe regions 42 upwardly during the cold heading process so that recessesarise at the corresponding positions 42. The designation “upwardly” isonly to be understood with reference to the illustration of FIG. 1 and,as are other statements of position in this application, only used inrelation to the Figures and do represent a spatial restriction of thesubject of the invention. The lugs 40 ensure that a cable shoe an besecured to the fastener element by means of a screw inserted from abovewithout the cable shoe rotating during attachment of the screw, since aco-rotation of the cable shoe is prevented by the lugs 40.

The cable shoe which represents an electrical terminal device can have aconnection surface provided as an eye which has a circular cut-out toreceive the said screw, or can have a—likewise known—U-shaped cut-outwhich is bounded by two terminal legs. In both cases a connection regionextending sideways away from the connection surface is provided whichholds a cable which is normally secured in current conducting manner tothis connection region via a crimped connection. The precise design ofthe electrical terminal device is however not restricted to suchembodiments and can in principle have any desired form including theform of sheet metal parts, for example sheet metal parts which projectout of a housing on the electrical apparatus, as is for example shown inFIGS. 15 and 16. It is only necessary for the form of the mount at thefastener element to be compatible with the form of the electricalterminal device so that the desired security against rotation isachieved.

As is evident from FIG. 4 the fastener element 10 has cylindrical freespaces or cut-outs 44 and 46 above and below the smooth cylindrical bore38 with these free spaces having, a diameter which is normallydimensioned to be fractionally larger than the outer diameter of a screwwhich is screwed into the cylindrical bore 38.

Although the cylindrical bore 38 is here arranged partly in the headpart 14 and partly in the guide section 18 of the fastener element 10 itcould also be fully arranged in the head part or fully arranged in theguide section.

FIG. 4 shows the fastener element 10 in a first stage of the attachmentto the sheet metal part 50, with the sheet metal part being supported inthe illustration of FIG. 4 on a die button 52 and being pressed againstthe die button 52 by means of a ring-like hold-down member 54, with thehold-down member 54 being preferably provided but not essential.

The illustration of FIG. 4 assumes that the attachment of the fastenerelement 10 to the sheet metal part 50 takes place in a press, with thedie button 52 being arranged in the lower tool of the press (not shown)and the fastener element being pressed by means of a likewisenon-illustrated setting head onto the sheet metal part 50, with thesetting head being able to be attached to an intermediate plate of thepress or to an upper tool of the press. Such setting heads and hold-downmembers 54 are well known in the prior art and will therefore not beespecially described here. It should, however, be noted that otherarrangements within a press are also possible. For example, the diebutton 52 can be arranged in an intermediate plate of the press with thesetting head, with or without a hold-down member, then being attached tothe upper tool of the press. It is also possible to provide the diebutton 52 at the upper tool of the press and to then mount the settinghead, with or without the hold-down member on an intermediate plate ofthe press or on the lower tool of the press, i.e. to attach the fastenerelement 10 in the reverse direction below the sheet metal part 50.

It is also possible to attach the fastener element 10 to the sheet metalpart 50 by a robot or by using a C-frame with pressure cylinder knownper se, with the robot or an auxiliary robot then holding the die button52 below the sheet metal part and serving for the application of therequired pressing force on the fastener element 10.

In FIG. 4 a two-part design of the die button 52 is shown. This consistsof an outer ring-like die part 54 and an inner likewise ring-like diepart 56 having a central longitudinal bore 58. In this example the innerdie part 56 has a slightly conically extending outer wall whichcooperates with a correspondingly shaped conically extending inner wall53 of the outer die part 54 so that the upper end face 60 of the innerdie part 56 lies below the upper end face 62 of the outer die part 54and hereby forms a recess 64. The upper end face 60 of the inner diepart 56 also forms the base surface of the recess 64 and has in otherrespects a ring-like concavely arched surface 66. The central bore 58 ofthe central die part 56 has a diameter which is fractionally larger thanthe outer diameter of the guide section 18. The recess 64 has a diameterwhich is somewhat larger than the outer diameter of the head part 14 ofthe fastener element 10 plus the double-thickness of the sheet metalpart 50.

Both the inner die part 56 and also its bore 58 and also the outer diepart 54 and the recess 64 defined between the two die parts are disposedcoaxial to the central longitudinal axis 11 of the fastener element 10.The die button 52 could also be made in one-part form.

Starting from the stage of FIG. 4 the fastener element 10 is now pressedtowards the sheet metal part 50 in accordance with FIG. 5 by theapplication of a force in the arrow direction 70 onto the upper end faceof the fastener element 10 by means of the setting head, for example inthe press, or by using a robot and with simultaneous support of the diebutton, with the hold-down member 54 which is optionally provided inFIG. 5 being omitted for the sake of the illustration.

One sees that the guide section presses the sheet metal part against theupper end face 60 of the inner die part 56 and has drawn the sheet metalpart into a conically extending recess 72. At this stage the ring-likecutting edge 28 of the guide section formed as a piercing section 18 hasnot yet started to cut through the sheet metal part 50 and the freelower end face 22 of the rivet section 16 has not yet contacted thesheet metal part 50.

In the further stage of FIG. 6 the guide section 18 has separated apiercing 5 slug 74 from the base of the conical recess of the sheetmetal part and partly pushed this through the central bore 58 of thedie, with the central bore 58 also being able to made so that itdiverges slightly downwardly, so that the piercing slug can be disposedof through this central longitudinal bore by gravity, optionally with.pneumatic assistance.

After the cutting out of the piercing slug the rounded outer wall 64 atthe free end of the rivet section 16 has also pressed the wall of theconical recess of the sheet metal part 50 away from the centrallongitudinal axis 11, i.e. brought the wall into a somewhat steeperposition, and has dilated the hole 76, which has arisen by the cuttingout of the piercing slug 74, to such an extent that the free end of therivet section 16 can now be pushed through the hole 76 so that the innercurved wall 26 of the free end of the rivet section can enter intocontact with the ring-like recess 66. In this way, with a furtherdownwardly directed movement of the fastener element as a result of thepressure in the arrow direction 70, the tubular rivet section 16 isbeaded over in accordance with FIG. 7 to form a rivet bead 78. Throughthis beading over process the sheet metal. part 50 is so deformed in theregion of the previous conical recess that it is clamped in form-fittedmanner between the ring-like contact surface 12 and the beaded overrivet section. At the same time the noses 30 providing security againstrotation are pressed into the sheet metal part so that a securityagainst rotation also arises. When the features providing securityagainst rotation are formed by corresponding recesses the sheet metalmaterial is pressed into such recesses whereby a security againstrotation likewise arises.

The sheet metal part is however simultaneously partly pressed into therecesses 42 which have arisen by the formation of the lugs 40 so that asecurity against rotation also arises in this region. Should the headpart 14 of the fastener element 10 have a polygonal or grooved or ribbedshape then a corresponding form-fitted connection between the sheetmetal part and the fastener element is also produced in this region.

One can see from FIG. 7 that the guide section 18 extends ever deeperinto 10 the central bore 58 of the inner die part 56 during theattachment of the fastener element 10 whereby a secure guidance of thefastener element is achieved. The finished component assembly consistingof a fastener element 10 and 15 a sheet metal part 50 is then shown inFIG. 8 after removal from the attachment 2, i.e. from the press or fromthe robot or from attachment tools which are conceived differently.

One can see that the guide section projects clearly beyond the beadedover 20 rivet section 16. It is in other respects also possible todimension the arrangement such that the body part 14 is accommodatedstill further within the recess in the sheet metal part or indeed fullywithin this. In the finished state in. accordance with FIG. 8 acomponent assembly can be provided as a whole with a protective coatingand an electrical terminal device, for example a cable shoe cansubsequently be attached to the upper end thee of the fastener elementor onto the lower end face of FIG. 8, i.e. the corresponding cutting orthread forming screw can be introduced coming from the top into thecylinder bore with simultaneous formation of the thread cylinder. Thelugs 40 which. are provided here, make it possible to use the element asan electrical terminal element, for example as an electrical groundingelement in a vehicle body.

The fastener element 10 in accordance with the present invention has the5 special advantage that it can also be used with sheet metal parts 50provided with protective layers or paint layers and neverthelessproduces an excellent electrical connection and indeed in the region ofthe pierced hole and of the noses providing security against rotationwhich, particularly with a sharp edged design of the noses providingsecurity against rotation locally cut through the protective coating andensure a metallic connection to the sheet metal part 50. Moreover theprotective layer is damaged at points which lie within the form-fittedconnection between the sheet metal part 50 and the fastener element sothat a seal is present and corrosion is prevented. The form-fittedconnection between the sheet metal part and the fastener element is sointensive that the connection represents a sealed connection which, if aparticular seal is necessary, can also be assisted by the application ofan adhesive to the element or to the sheet metal part. Through therecess in the sheet metal part 50 in the region of the fastener elementan excellent connection to the sheet metal part is ensured so that ahigh resistance against pull-out forces in both directions and a highbutton out resistance is generated and, moreover, a high resistanceagainst shear forces and torsion forces is present. In addition, theelement can be used with alternating dynamic loadings and fatigueeffects with dynamic loadings need not be feared.

The FIGS. 9 to 15 relate to a further embodiment of a fastener element10 in accordance with the invention which is very similar to thefastener element of FIGS. 1 to 8. There are essentially only twodifferences which will be described somewhat later. The same referencenumerals are used for the embodiment of FIGS. 9 to 15, and also for thefurther figures, as for the first embodiment in accordance with FIGS. 1to 8 and it will be understood that parts or features which have thesame reference numeral have the same function as in the firstembodiment. Insofar the previous description also applies to thefollowing examples, unless something to the contrary is stated.

As mentioned, in the embodiment of the fastener element of FIGS. 9 to15, there are basically represents mainly two differences with respectto the previous embodiment in accordance with FIGS. 1 to 8. In onerespect this refers to the ring-like contact surface 12 which in thisexample is conically arranged and forms an included cone angle of 90° atthe central longitudinal axis 11 of the fastener element. The featuresproviding security against rotation are located in this exampleexclusively in the region of the ring-like contact surface 12. Thefastener element 10 of the embodiment of FIGS. 9 to 15 is attached inprecisely the same manner to a sheet metal part as in the firstembodiment except that the die button is slightly modified in order totake account of the conical contact surface. Further particulars of theadvantages and designs of the fastener element with a conical sheetmetal contact surface can be found in the PCT application PCT/EP02/04365of the present applicant.

The second distinction lies in the fact that the mount 80 for receivingthe electrical terminal device 104 is formed in this example by aprojection 41 which projects away from the upper end face of thefastener element 10 which is remote from the rivet section 16. Thisprojection has a central bore which lies coaxial to the central bore 38of the hollow fastener element 10 and has a somewhat larger diameterthan the bore 38. In its external outline the projection is in thisexample eight-sided, i.e. octagonal and serves to receive an electricalterminal device 104 which can be seen from FIGS. 15 and 16. Accordingly,the electrical terminal device is formed as a sheet metal part with acut-out 110 in the form of a passage hole through which the screw 106projects and has three lugs 112 which project downwardly in theillustration of FIG. 15, which respectively contact one of the sidesurfaces of the projection, which is of octagonal shape in its externaloutline. The lugs 112, as well as the hole 110 and any other features ofshape of the sheet metal part 104, such as for example external outline,are produced by a punching process, with the lugs 112 being formed frommaterial which is exposed at three sides from the regions 114 by thepunching process and bent downwardly. In this example, in accordancewith FIGS. 15 and 16, the electrical terminal device 104 is provided asa terminal clamp of a housing 116 of an electrical unit of any desiredform of construction. The electrical terminal device 104 could, however,just as well be provided with a cable connection region to which one ormore cables is or are secured by crimped connection. For example theregion 118 could serve for this purpose.

The exposed surfaces of the component assembly consisting of the sheetmetal part 50, the fastener element 10 of FIG. 15 including the outersides and the upper end face of the projection 41 are, as also in otherexamples of the component assembly, coated with a protected coating 120(only indicated at certain positions and not shown in FIG. 8).Nevertheless a high quality electrical connection is present between theelectrical terminal device 104 and the sheet metal part 50 and indeedthis connection passes from the electrical terminal device via the headof the screw 106, the shaft part of the screw 106 and the thread formedor cut into the fastener element by this screw and further via thefastener element itself and the features providing security againstrotation and the pierced surfaces into the sheet metal part 50. Theprotective coating at the surface of the projection 41 thus does notprevent a high quality electrical connection being achieved.

Finally, reference is made to the further embodiment of the invention inaccordance with FIGS. 17 to 19. Here also, as explained above, the samereference numerals are used for the same parts.

The fastener element 10 of FIGS. 17 to 19 is formed in accordance withthe European Patent EP 0 539 793 except that here the rivet section 16is formed as a piercing and riveting section in accordance with thedescription of DE 3446978 C or DE 3447006 C.

Amount 80 for an electrical terminal device is present at the free endface of the fastener element 10 of FIGS. 17 to 19, i.e. at the end facewhich is remote from the piercing and riveting section 16 and is formedin accordance with the mount 80 of the embodiment of FIGS. 9 to 15. Itthus has a projection 41 which is octagonal in its external outline.Naturally the fastener element 10 in this example could also be providedwith two lugs corresponding to the lugs 40 of the embodiment of FIGS. 1to 8.

The present invention is not restricted to the fastener elements whichare 20 shown in the Figures but rather any hollow fastener element whichcan be attached to a sheet metal part with an adequately high securityagainst rotation and security against button out can be used inaccordance with the invention by the provision of a corresponding mountfor an electrical terminal device.

The fastener elements described here can for example be manufactured inall materials which achieve the strength class 5.6 or higher. Suchmetallic materials are normally carbon-steel with 0.15 to 0.55 carboncontent.

In all embodiments all materials can be named as an example for thematerial of the fastener elements which achieve the strength values ofclass 8 in accordance with the ISO standard in the context of colddeformation, for example a 35B2 alloy in accordance with DIN 1654. Theso formed fastener elements are suitable amongst other things for allcommercially available steel materials for sheet metal parts of drawingquality as also for aluminium or its alloys. Also aluminium alloys, inparticular those of higher strength, can be used for the fastenerelements for example AIMg5. Also fastener elements of higher strengthmagnesium alloys such as for example AM5O can also be considered.

The invention claimed is:
 1. Method for producing an electricallyconductive connection between an electrical terminal device having acut-out and a sheet metal part, the method comprising: rotationallyfixedly riveting to the sheet metal part a hollow fastener elementexecuted with two projections which are formed by two lugs having aspacing from one another and which are arranged to the side of a bore ofthe hollow fastener, an electrically conductive connection thereby beingproduced between the fastener element and the sheet metal part;subsequently providing the so-manufactured component assembly with anelectrically non-conductive or poorly-conductive protective coating,wherein a mount for the electrical terminal device is formed by said twolugs in the region of the end face of the fastener element to which theelectrical terminal device is attached and prevents a rotation of theterminal device relative to the fastener element and the sheet metalpart; and screwing a thread-forming or thread-cutting screw through thecut-out of the electrical terminal device and into the hollow fastenerelement, forming or cutting therein a thread by the screw-in movement.2. Method in accordance with claim 1, wherein the fastener element isattached to the sheet metal part so that it is secure againstbutton-out.
 3. Method in accordance with claim 1, wherein the fastenerelement is self-piercingly attached to the sheet metal part.